Depending on how the received GPS signals
from various GPS satellites is processed, receivers can be classified as 1.
Parallel Channel Receivers, and 2. Multiplexing Receivers.
Parallel Channel Receivers
The parallel channel receiver locks onto
different GPS satellites simultaneously, and provides un-interrupted signals
to the GPS processor. Due to continuous tracking of the satellite signals,
the accuracy and time to lock on to the satellite signals are better
compared to multiplexing receivers. Atleast four hardware radio channels are
required for continuous operation. . Recent GPS receivers have sufficient
hardware radio channels (upto 12) to lock onto all the satellites that
happen to be in view at any time.
Multiplexing Receivers
The multiplex receiver switches between
satellites being tracked, thus establishing a temporary contact with one or
two satellites and switches to other satellites to get the information
required. Since a multiplexing receiver locks on to a satellite for only a
short amount of time, they tend to be less accurate than parallel channel
receivers. On the otherhand, parallel channel receivers lock on to a given
satellite, and stay with the same as long as required. The signal
acquisition process (also called triangulation) is said to be better with
parallel channel receivers. A 12 channel parallel channel receiver will be
able to simultaneously track up to 12 satellites in the orbits.